Fix a final (?) task field issue which slipped through the cracks
Summary:
Derped this one up; while my testing was successful in preventing runaway
attaching I missed the bit where it doesn't actually work.
This resolves the "Unknown Object" link seen on T661.
Test Plan:
- Created two new revisions, each attached to a local task.
- Verified that they attached additively, Maniphest and Differential were
linked to the right places, and nothign else bad happened.
Reviewers: btrahan, fratrik
Reviewed By: fratrik
CC: aran, fratrik, btrahan
Differential Revision: 1181